Current EUV lithography technology suffers from inadequate source power. For commercially viable EUV lithography, 1 kW (1000 W) of EUV power at the intermediate focus (IF) is required. Unfortunately, to date only about 50 W has been achieved.
Current EUV source systems use a pulsed IR laser driver in conjunction with a Sn droplet target and a multilayer coated normal incidence collector (NIC). Unfortunately, scaling this source system to high EUV power (e.g., 1 kW at the IF) is prohibitively difficult. In particular, to obtain 1 kW EUV power at the IF requires a drive laser power in excess of 100 kW at the Sn target, along with pulsed laser synchronized to hit the Sn droplet targets (operating at about 100 kHz), which is extremely demanding. Furthermore, the laser-target interaction physics in the current scheme produces high levels of reflected IR laser power from the LPP, resulting in reduced conversion efficiency from laser power to EUV power. This also poses the risk of damage to downstream optical components and the wafers. At high power, the debris from the LPP puts the NIC at serious risk of being damaged very quickly. All these problems scale at least linearly with the increase of EUV power at the IF.